The present disclosure relates generally to optical detectors. More specifically, the present disclosure relates to defects in Focal Plane Arrays (“FPAs”) found in an optical system.
FPAs are detectors that have a linear or two-dimensional matrix of individual elements (e.g., pixels), and are generally used at the focus of optical systems for capturing images or video, but can also be used for other non-imaging purposes such as, for example, spectrometry, LIDAR, wave-front sensing, thermal imaging, medical imaging, as a receiver of a radio telescope, etc. Materials used to form sensory portions of an FPA are selected based upon wavelengths of light that are desirably absorbed and/or detected. The materials have respective band gaps, wherein a band gap of a material corresponds to wavelengths of light that can be absorbed and/or detected by the material. For example, a camera that desirably detects light in the visible spectrum (˜380 nm to ˜760 nm) may utilize an FPA comprising Silicon (“Si”) or Si-based materials that have band gaps that correspond to the visible spectrum.
Defects or impurities in sensory materials can cause the FPA to comprise defective pixels, which can in turn negatively impact overall operability and performance of the FPA. Conventionally, however, defects in a sensory layer of the FPA are indiscernible until a read-out circuit is hybridized with the sensory layer (e.g., the defects are not detectable until manufacturing of the FPA is completed). Thereafter, if the FPA does not operate as expected (e.g., the FPA has too many defective pixels), the FPA is discarded. For FPAs comprising relatively inexpensive material, cost of manufacturing FPAs is relatively low. For FPAs comprising relatively expensive material, however, costs of the FPA may be relatively high. Thus, for some types of FPAs, discarding a defective FPA and manufacturing a new FPA is impractical.